The invention relates generally to fastener drive tools, and more particularly to anvil-type or hammer drive, powder actuated tools.
Many types of fastener drive tools and like explosively actuated equipment have been developed over the years, and such tools have generally had complex mechanisms for firing pin operation, for ejecting or extracting spent cartridge shells and for meeting safety standards. Recent developmental trends are toward improved low velocity tools of the type in which a piston ram member is explosively driven to actuate a nail or like fastener into a workpiece such as concrete or wood. One type of low velocity tool is described in U.S. Pat. No. 3,066,302, which tool uses a pistol-type firing pin mechanism having a trigger and sear to trip a spring-loaded firing pin that is cocked by compressing the muzzle end of the tool telescopically rearwardly within the tool housing. Many such pistol-type low velocity tools are disclosed in the prior art.
Another type of low velocity tool is described in U.S. Pat. No. 4,025,029, which tool, like the present invention, is a hammer-activated, powder actuated stud driver. Such hammer drive tools are conventionally operated by placing the muzzle end of the tool against the workpiece and striking the rear end of the tool with a hammer to fire the cartridge or like powder charge. Hammer drive tools heretofore, while simple in construction and operation, have been inherently dangerous due to the fact that a loaded tool could be fired if accidentally dropped. U.S. Pat. No. 3,688,964 discloses another low velocity hammer drive tool designed for caseless powder loads and having some safety features.